The Twin Cities reached the highest heat index value of the year so far at 5pm tonight. The temperature at MSP was 91 with a tropical dew point of 78. That makes an oppressive heat index of 106 degrees in the metro!

It appears the line of storms west of the metro may fade this evening, but a severe thunderstorm watch remains in effect. If storms do not develop, NWS may cancel portions of the watch early this evening. Most of the tornadic and severe weather dynamics have shifted east into Wisconsin tonight.

A cool front will pass thorough later tonight bringing relief in the form of cooler temps and much lower dew points in the 50s by morning.

Stay cool!

PH

Update 4:45pm:

New severe thunderstorm watch includes the Twin Cities until 10 pm tonight. One more line of storms may deveop and move toward the metro this evening.

More damage reports from storms moving through Wisconsin, including trees down in Menomonie.

MPX: Lakeville [Dakota Co, MN] law enforcement reports TORNADO at 02:40 PM CDT — tornado reported by law enforcement in southern lakeville. another report of a tornado from 2 miles s of lakeville at intersection of interstate 35 and hwy 19. vehicle blown off road in that location.

BULLETIN – IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WARNING

NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN

211 PM CDT WED JUL 14 2010

THE NATIONAL WEATHER SERVICE IN THE TWIN CITIES HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR…

CENTRAL DAKOTA COUNTY IN EAST CENTRAL MINNESOTA…

SOUTHEASTERN SCOTT COUNTY IN EAST CENTRAL MINNESOTA…

* UNTIL 300 PM CDT

* AT 209 PM CDT…RADAR INDICATED A SEVERE THUNDERSTORM…CAPABLE OF

PRODUCING QUARTER SIZE HAIL AND DAMAGING WINDS IN EXCESS OF 60 MPH.

THIS STORM WAS LOCATED 5 MILES WEST OF NEW MARKET…OR ABOUT 22

MILES NORTH OF FARIBAULT…AND MOVING NORTHEAST AT 35 MPH.

Update 2:15pm:

Heavy storms developing in eastern metro and south heading into Dakota and Goodhue counties. be alert for downpours, hail, lightning and possible damaging winds.

DLH: Cloquet [Carlton Co, MN] law enforcement reports TSTM WND DMG at 09:25 AM CDT — many tree limbs down…power lines down…and a few trees downed in and around the city of cloquet.

Update: 9am

Tornado Watch issued until 4pm includes metro and much of eastern Minnesota & western Wisconsin.

(click for bigger image and cities)

We don’t say this often from the weather lab, but today is one of those days to keep a close eye on your plans and kids, and be ready to seek shelter if severe storms approach your location.

All the necessary ingredients appear to be coming together for what could be a significant severe weather and tornado outbreak from the Twin Cities area south and east. Here are some of the parameters that are coming together today.

1) Deep tropical moisture:

Dew points are in the 70s and may approach Amazon Jungle levels near 80 degrees today.

2) Unstable air mass:

A cold front and cooler air aloft will create rapidly rising air to generate storms easily today.

3) Strong wind shear:

Winds are turning with height in the atmosphere today. This means storms will rotate, and strong low level wind shear means that rotation can translate to ground level. That’s an ideal situation for producing tornadoes. SPC is concerned about the potential for strong (EF2 and higher) tornadoes in Minnesota and Wisconsin today.

Violent updrafts within storms over 100 mph will carry hail high into the atmosphere today. There is the potential for golf ball to even baseball sized chunks of hail falling form the sky this afternoon.

5) Cold front approaching:

The timing of an approaching cold front means that storms may explode right overhead in the Twin Cities metro this today.

The bottom line is expect severe weather today. The greatest threat for tornadoes appears to be from the Twin Cities area south and east. This includes Mankato, Owatonna, Waseca, Northfield, Red Wing, Rochester, Albert Lea, La Crosse and Eau Claire.

Expect storms today to contain the potential for damaging winds, large hail, and flooding rains as they move through.

About the blogger

Paul Huttner is chief meteorologist for Minnesota Public Radio. Huttner has worked TV and radio stations in Minneapolis, Tucson and Chicago. Paul is a graduate of Macalester College in St. Paul and holds a bachelor’s degree in geography with an emphasis in meteorology.

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what happened to the dampening affects of the light cloud cover this AM? Or is that just plain not enough to counteract the energy in the system? I ran from 5:40 to about 6:20 this AM; the humidity was shockingly high, making for a wet run, despite pleasant temps.

jeanette

It would have been helpful to see this before I picked out my blouse and left the umbrella in the closet.

Paul Huttner

Hi B:

Yes, there is just too much insability to limit the (so far) non severe storms near the metro. If we get more sun today, things could get busy in a hurry this afternoon.

Hi Jeanette:

We’ve been talking about likely storms today since Monday. Hopefully that was plenty of lead time?

PH

jeanette

I’m most certainly the fool today!

Paul Huttner

No way you’re a fool Jeanette. Here’s hoping you can walk between the raindops today!

PH

Jill

You may have explained this before, but what’s a “derecheo”?

Thanks.

Bruce Sach

Is there a site to show what the radar looked like before, during and after a storm comes through?